This invention relates to use of an ink cartridge in printing apparatus and in particular to control of use of inkjet or other replaceable ink cartridges in postage meters.
Known inkjet cartridges include an inkjet print head and an ink reservoir integral therewith. In use of the cartridge to print impressions, ink is ejected from nozzles of the print head to print the impressions and is replenished from the ink reservoir. Over a period of operation of the cartridge, the amount of ink contained in the ink reservoir is gradually depleted until eventually the reservoir is incapable of replenishing the ink in the print head. When the reservoir is depleted to an extent that imprints of a desired quality cannot be printed by the print head of the cartridge, the entire cartridge is removed from the printing apparatus and is replaced with a new cartridge in which the ink reservoir is full of ink.
In some applications of use of inkjet cartridges, for example output printers for personal computers, there is no stringent requirement regarding the quality of the imprints obtained and the cartridge may be continued to be used until such time as the user decides that the print is becoming illegible. However in other applications of use of inkjet cartridges where a fully legible record of a transaction or other event is required it is desirable to provide a control of use of the cartridge such that the quantity of printing effected by the cartridge is limited and hence the cartridge cannot be used when the ink in the reservoir is so depleted that imperfect imprints are obtained. One application where a fully legible printed record of a transaction is required is in postage meters. Postage meters are required to carry out accounting operations in respect of postage charges in respect of mail pieces and to print a postal indicium on each mail piece providing evidence of the amount of postage charge applied to the mail piece and that accounting in respect of that specific postage charge has been effected. The postal authorities issue regulations determining the form and content of the postal indicia and also determining the minimum acceptable print quality of the printed postal indicia. Providers of postage meters are required to supply postage meters that inter alia print postal indicia with a quality that at least meets the minimum requirements at all times of operation of the postage meter.